I really dont see why random numbers should be predictable.
Because you're asking a computer (that is a Finite State Machine) to generate them. Thus it is impossible to get truely random numbers. The only reason they appear random, is because we aren't good enough at large scale pattern matching. Also yes, there are no truly random numbers in computers unless maybe you figure in some real-world input such as the time of day or whatever, which is likely to be at least slightly different each time.
Even then it would still not be entirely random.Still isn't it as easy to test as try the same program on a Mac and PC and see what the results are?